Answer

Pepto Bismol will firm his stool up. I had the exact same issue with my dane Thor. I gave him 2 chewable tabs a day. He wouldn't eat them without putting some peanut butter on them but once he did his stool returned to normal. It took around two weeks and then I was able to take him off the Pepto. You will see results within 24 hours

Canned Pumpkin (Not Pie Filling) will help with the stool if it's a temporary thing. 2x boiled chicken breast will flush out their digestive track. A probiotic tablet will correct unbalanced digestive enzymes. If all else fails put the dog on the raw meat diet (AKA B.A.R.F.) and if that works then you know they are allergic to kibble.

We have learned with our female great dane who has had diarrea often that it was the content of her food that was causing it. It was the chicken and the fillers they use in the dog food. Corn also made her lose her hair. We have been using lamb meal and rice and nothing else and that has made a huge difference. As long as that is the only thing she eats she is fine, any table scraps or raw hides or ham bones most of all and again anything with chicken in it will cause her to have loose stools.